<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>天下第一帅</title>
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
    <script>
        const $ = document.querySelectorAll.bind(document);//可以这样直接把this指向document
    </script>
</head>
<body>
<form action="form.php" method="get">
    用户名: <input type="text" name="username"> <br>
    密码: <input type="password" name="pad" id=""> <br>
    <input type="submit" value="提交">
</form>
</body>
</html>